Non-staining aluminum rolling



NON-STAINDJG ALUMINUM ROLLHJG LUBRICANT John J. Plemich, Whiting, Ind., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application March 29, 1956 Serial No. 574,589

'1 Claim. (Cl. 252- 56) This invention relates to the avoidance of staining of aluminum sheet by lubricant employed in the rolling operation which is usually effected at a temperature of about 600 to 650 F.

Many types of compounds have been employed as lubricants in the rolling of aluminum sheets but most of them either provide inadequate lubrication or result in an objectionable stain or imperfection on the surface of the resulting sheet. One of the best aluminum rolling lubricants heretofore known was a low boiling petroleum distillate containing a high molecular weight polybutene (U.S. 2,256,603). The object of this invention is to provide an improvement in this type of lubricant, i.e. to provide an effective aluminum rolling lubricant of improved nonstaining characteristics.

I have discovered that an undiluted polybutene which has a viscosity in the range of about 40 to 80 seconds Saybolt at 100 R, which contains no components boiling as high as 650 F. and which has an average molecular weight below 300 and preferably in the range of about 200 to 270, when it is subjected to the standard aluminum stain test is remarkably superior to polymers of higher viscosity and molecular weight and to blends of such polymers in conventional low boiling mineral oil, such as mineral seal oil. The oil film that remains on an aluminum sheet after it has been rolled with this improved lubricant does not cause staining of the aluminum even in a subsequent annealing step.

The procedure for testing the stain properties of aluminum rolling lubricants is substantially as follows: about .8 mil. of the lubricant to be tested is carefully spread over the entire surface of a clean aluminum test plate which is then placed in an electric mufile furnace where it is held at a temperature of about 650 F. for a period of about 30 minutes, the test plate being horizontally placed so that the lubricant will not run oif. At the end of the test period the plate is removed and compared with standard plates which are rated from A to H, the A plate being bright and free from stain and the H plate being most stained.

Test data obtained on a series of lubricants is shown in the following table:

Patented Aug. 11, 1959 The test data show that high viscosity and high molecular weight polybutenes per se (tests a and b) are unsatisfactory as aluminum rolling lubricants; although such polymers have the known properties of decomposing without substantial carbon formation at high temperatures, they nevertheless cause undesirable staining of aluminum at 650 F. Mineral seal oil, which might be expected to vaporize completely at 650 F., nevertheless causes appreciable staining either when employed alone (test g) or with a viscous and high molecular weight polymer (test h). The low molecular weight polybutene of lubricating oil viscosity (tests d, e and f) in the absence of mineral oil diluent proved to be outstandingly superior to any of the other lubricants tested. For best nonstaining properties it appears that the polybutene should have a viscosity below 100 seconds Saybolt at 100 F. (run 0 showed a stain test of B). Ordinary commercial polybutene of 100 seconds Saybolt viscosity at 100 F. has an average molecular weight of about 330 and contains substantial amounts of components boiling upwards of 650 F.; apparently it is these high molecular weight, high boiling components which are responsible for stain and it is therefore important that the polybutene used as an aluminum rolling lubricant be free from components boiling above 650 F., i.e. it should boil in the range of about 460 to 645 F.

Similar tests made at 600 F. showed the 40 and 50 vis. materials (1 and e) to have stain ratings of A, the vis. polymer (d) to have a stain rating of about B and the vis. polymer (c) to have a stain rating of D. Here again the materials of about 40 to 80 seconds Saybolt viscosity at about 100 F. were found to be outstandingly superior to heavier polymers.

As a specific example, an aluminum rolling lubricant has been successfully tested which has a viscosity of 80 seconds Saybolt at 100 F., a boiling range of 560 to! 645 F., a flash point of 310 F., and an API gravity of 38.8, this particular lubricant having an average molecular weight below 270 and being substantially free from components boiling above 650 F. In the actual rolling of aluminum an effective amount of a non-staining lubricity agent, e.g. about 1 percent of butyl stearate is added to the polybutene.

The polybutenes herein referred to are those prepared by polymerizing butenes from a butane-butylene stream as described, for example, in US. 2,407,873, and 2,677,000-1-2.

I claim:

A non-staining aluminum rolling lubricant which consists essentially of an undiluted polybutene, prepared by polymerizing butenes from a butane-butylene stream, which polybutene has a Saybolt viscosity at 100 F. in the range of about 40 to 80 seconds, which boils in the range of about 460 to 645 R, which has an average molecular weight in the range of about 200 to 270, and which polybutene contains about 1 percent of butyl stearate.

References Cited in the file of this patent UNITED STATES PATENTS 2,256,603 Wright Sept. 23, 1941 2,403,238 Rosenstiehl July 2, 1946 2,407,873 Evering et a1 Sept. 17, 1946 2,590,451 Perry Mar. 25, 1952 2,605,224 Jahn July 29, ,1952 2,652,362 Woods et a1. Sept. 15, 1953 2,729,992 Wankat Jan. 10, 1956 

